It is well known that a hydrocarbon fluids such as crude oil or residual oil deposit asphaltenes during production and/or use. In the example of a crude oil, asphaltenes are maintained in a stable colloidal dispersion in the hydrocarbon fluid under the temperature, pressure, composition and environmental conditions found in the oil bearing reservoir. However, when the temperature or pressure are reduced, e.g., during extraction from an oil reservoir, changes in composition (loss of gas and other light components) largely due to pressure and temperature changes enables asphaltene molecules to agglomerate or otherwise precipitate out to form asphaltene deposits. The asphaltene deposits are capable of causing occlusion and ultimately blockage within the oil bearing strata or anywhere else along the production and storage system through which the oil passes or is stored, including any pipe, conduit or storage vessel. The occlusion reduces production rates such that it becomes necessary to mechanically remove the deposits, resulting in loss of production, down-time and increased engineering costs.
In the case of asphaltenic residual and heavy fuels, the destabilization of the asphaltene colloid is generally due to similar reasons, but also due to the addition of cutter stocks or in-tank mixing of different and incompatible batches of fuel, which can result in a hydrocarbon environment which does not maintain the stability of the asphaltenes. An example of this often seen in practice is when ships change over to low sulphur fuel for entry into areas where the use of high sulphur fuels is prohibited. Changing over to low sulphur fuel can destabilize the asphaltene resulting in asphaltene deposition in pipework and possible blockage of filters, etc. Therefore, it is important to efficiently disperse agglomerated asphaltenes in the bulk hydrocarbon, or to remove and/or inhibit the formation of asphaltene deposits to avoid blockage in a crude oil production system.
In the case of asphaltene deposition in refinery and other petrochemical plant applications, a hydrocarbon stream already containing asphaltenes can be formed in situ. In this case, the asphaltene deposition results in the formation of carbonaceous deposits in a process known as coking or fouling.
Therefore, asphaltene deposits are known to be capable of causing blockage to a number of applications involving a hydrocarbon fluid, and it is important to remove or inhibit the formation of asphaltene deposits to avoid blockage of an oil well or pipelines.
British Patent Application GB 2,337,522 discloses a carboxylic polymer capable of reducing asphaltene deposition formed from at least one of (a) an ethylenically unsaturated alcohol, carboxylic acid or ester, (b) an ethylenically unsaturated carboxylic ester with a polar group in the ester, and (c) an ethylenically unsaturated carboxylic amide. A preferred polymer is a alkyl (meth)acrylate.
International Publication WO 01/055281 discloses an inhibitor for asphaltene deposition employing a compound selected from a polyhydric alcohol reacted with a carboxylic acid, an ester or ether formed from a glycidyl ether or epoxide.
It would be desirable to have a method of asphaltene control in a hydrocarbon fluid. The present invention provides method of asphaltene control in a hydrocarbon fluid.